1. Field of the Invention
The present invention relates to an organic light-emitting diode, organic light-emitting diode substrate, and a method of manufacturing the same.
2. Description of Related Art
An organic light-emitting diode is a light-emitting element using organic electroluminescence (hereinafter, “electroluminescence” is abbreviated as “EL”). In general, the organic light-emitting diode has a configuration in which conductive layers (positive electrode conductive layer and negative electrode conductive layer) are provided on both surfaces of an EL layer, which includes a light-emitting layer containing an organic light-emitting material, respectively. As the EL layer, in addition to the light-emitting layer, an electron transport layer, a hole transport layer, and the like are provided as necessary. The organic light-emitting diode is largely classified into a bottom emission type in which a positive electrode conductive layer formed from a transparent conductive layer such as ITO, an EL layer, and a negative electrode conductive layer are sequentially formed on a transparent substrate such as a glass substrate, and light is extracted from a substrate side, a positive electrode top emission type in which a negative electrode conductive layer, an EL layer, and a positive electrode conductive layer are sequentially formed on a substrate, and light is extracted from a side opposite to a substrate side, a negative electrode top emission type in which a reflective layer formed from a metal, a positive electrode conductive layer formed from a transparent conductive material such as ITO, an EL layer, a transflective negative electrode conductive layer, and an auxiliary electrode layer formed from a transparent conductive layer are sequentially formed on a substrate, and light is extracted from a side opposite to a substrate side, and the like.
The organic light-emitting diode has advantages such as less viewing angle dependency, low power consumption, and very small thickness. On the other hand, there is a problem in that light extraction efficiency is low. The light extraction efficiency is a ratio of an amount of light, which radiates from a light extraction surface (for example, a substrate surface in the case of the bottom emission type) to the air, to an amount of light generated from the organic light-emitting material. For example, the light which is generated from the light-emitting layer radiates in all directions. Therefore, it enters a waveguide mode in which the majority of the light repeats total reflection at an interface between a plurality of layers, each having a different refractive index, and thus the light is converted into heat or radiates from a side surface while being guided between the layers. As a result, the light extraction efficiency decreases. In addition, the distance from the metal negative electrode conductive layer is small, and thus a part of near field light from the organic light-emitting material is converted into surface plasmon on the surface of the negative electrode and disappears. As a result, the light extraction efficiency decreases. The light extraction efficiency has an effect on brightness and the like of a display and an illuminating device which are provided with the organic light-emitting diode, and thus various methods have been examined for improvement thereof.
As a method of improving the light extraction efficiency, a method of using surface plasmon resonance is suggested. For example, Japanese Unexamined Patent Application, First Publication No. 2002-270891, Japanese Unexamined Patent Application, First Publication No. 2004-31350, Published Japanese Translation No. 2005-535121 of the PCT International Publication, and Japanese Unexamined Patent Application, First Publication No. 2009-158478 disclose methods of providing a one-dimensional or two-dimensional periodic microstructure on the surface of a metal layer (negative electrode conductive layer). The periodic microstructure formed on the surface of the metal layer functions as a diffraction lattice, and converts surface plasmon into propagation light on the surface of a negative electrode. According to this, energy that disappears as the surface plasmon is extracted as propagation light to the outside of an element, and thus the light extraction efficiency is improved.
Among these Patent Documents, Japanese Unexamined Patent Application, First Publication No. 2009-158478 discloses a method in which a substrate having a periodic lattice structure due to a concavity and convexity is prepared according to a dry etching method using a two-dimensional crystal body constituted by a particle single layer film as an etching mask, and a positive electrode conductive layer, a light-emitting layer, and a negative electrode conductive layer are sequentially laminated on the substrate. In the method, the periodic lattice structure on a substrate surface is sequentially transferred during lamination, and thus a periodic lattice structure having a shape copied from the periodic lattice structure of the substrate surface is formed on the surface of the negative electrode conductive layer on a light-emitting layer side.